Back in the 1980’s there was a bit of a craze for using terracotta. It was everywhere, in magazines, on TV, and it was soon being used extensively in homes and also in commercial properties like pubs and wine bars. After a few years it seemed to disappear almost as fast. This is due in part to the over-exposure and the ever changing fashions for interior design, but I also suspect that more than a few people experienced a number of headaches in terms of sealing, cleaning and maintaining it.However, all things work in circles right? Well not exactly, but I do see that Terracotta is making a little bit of a come back, not like the last time, but people are it seems one again being swayed by the rustic charms and warm tones and using it in selected areas.
So, I though it timely to do a little article on the methods for sealing terracotta. There are basically two systems (and lots of variations for both) :
1. The traditional oil & wax treatment, or,
2. The modern, synthetic approach.
1. Traditional Oil & Wax.
Many Tilers still prefer this method, largely I think because this is the method they were taught. One of the most popular methods for sealing terracotta is to use a combination of boiled linseed oil and then polish with a neutral Beeswax.
First the tile is treated with several coats of boiled linseed oil; the oil is spread with a cloth or sponge as evenly as possible over the terracotta, before grouting. The first coat is the hardest as the oil is pulled into the extremely porous tile very quickly, so it takes a bit of skill and practice to get an even coat. Subsequent coats are a little easier, until the tile approaches saturation. Care must be taken not to over-apply the oil, making sure any surplus is not left to dry, as this would become sticky and require scraping off. Once the tile is sufficiently sealed (it will take several coats) it will also be considerably darker. It is the oil that gives terracotta that characteristic amber shade that many people like. Once dry, they can be grouted. When the grouting is completely dry, the tiles can be finished off with a coat or two of wax polish – there are many to choose from, some in paste form that require thinning with white spirits (a messy job) and others that come ready to use as a ‘floor wax’.
The advantage of this system is really just aesthetic, if you like that ‘warm look’ then go for this. However, there are several drawbacks: It is a much more involved process in the beginning; ongoing maintenance is also more arduous, the wax will quickly dull through traffic and cleaning, thus it will require frequent re-polishing and this is a hands and knees job, unless you are prepared to purchase a buffing machine. After a while, the wax will build up in layers and will start to actually attract and hold dirt, becoming darker and even tacky to the touch. At this point it needs stripping off, right back to the tile surface using solvent stripers (the oil will not be removed) and the whole polishing process starts again.
2. The Modern, Synthetic Approach
While possibly not offering quite the same depth of colour as oil and wax (it should be pointed out that not everyone likes that artificially darkened colour anyway) is much simpler and far easier to maintain. Again there are several propriety products available. Water-based, acrylic type coatings sealers are safe and relatively easy to use, offering both a surface seal and a degree of shine or gloss in one operation. This saves both time and money. Typically several coats of this type of product can be applied to the tile, depending on its porosity and the degree of sheen you are after. After grouting another coat may be applied. And that is it, job done. As it is a surface coating, just like wax it will of course wear, but it is more resilient and will not dull quite so quickly. With proper care, using neutral cleaners it can actually last for up to 3 years, but typically will not require any topping up before 12 months (this is dependent on many things of course). When it does start to dull down, there is no need to strip; instead a fresh coat can be applied right over what is already there.
If a very glossy finish is required, like a highly buffed wax, then adding a coat or two of a sacrificial acrylic polish on top of your coating sealer will add that high-gloss look. In addition to this, as it is also a sacrificial layer, it helps to protect and prolonging the life of the sealer beneath.
Copyright Ian Taylor and The Tile and Stone Blog.co.uk, 2013. See copyright notice above.
Hallo Ian
Thank you for all the info, I find it very helpfull.
I am “re-sealing” my clay tiles on my stoep. Do I apply the linseed/terpentine-mix on the grout between the tiles too?
Kind regards
Hi,
Sure, as long as you have prepared the surface of the grout also, (removed/cleaned traces of dirt, loose or old sealer etc). The grout should be treated the same as the tiles.
Just check, as they have been previously sealed, that there is enough porosity for the oil to penetrate, if it just sits on the top and does not go in then you have not stripped it sufficiently and it will just pool and make a mes on the surface.
Hope that helps
Ian
Good info,my question is will putting the linseed oil on the tiles before grouting stop the grout from adhering to the tile,regards patrick
Hi Patrick,
Yes, as I say in the article (I had to re read it as it is now years old!) Apply some oil before grouting. Basically the more coats of the linseed oil you can get on before grouting the better, as it pre-seals the tiles making grout clean-up much easier.
Hope that helps
Ian
I put linseed oil on mine. But in a few years it needed removing cos it got tacky. Best thing I found was oven cleaner. Put it on and leave for a few hours before removing.
Hello,
I have terracotta (Zia tile ‘cotto’) in my kitchen. After installation, we applied a penetrative ‘sealer’, but I would now like to apply an acrylic topcoat, since the penetrative sealer is not great and the tiles (which were not sealed in any other way) are getting stained. Can you recommend a safe, low-VOC, acrylic sealer for this purpose? Ideally it would provide a little color enhancement (to mask any of the existing staining) and a satin finish.
Thanks!
K.
I wonder if it is possible to use linseed oil in combination with synthetic wax?
Thanks for the information. I’m looking into installing unglazed zellige in my house. Can you recommend a good synthetic water-based acrylic sealant that might be available in Spain? Thank you!
Can’t see why not as long as the Linseed is allowed to dry first
Hope that helps
Ian
HI,
I think any sealer company which operates in Spain should have one, Lithofin, Fila, perhaps?
Hope that helps
Kind regards
Ian
Hi,
It can be tricky adding a top coat depending on the impregnating sealer used, some top coat sealers will be repelled or not lie ‘flat and even’ and dry with ridges or blisters. I would start with a good deep clean, with an alkaline cleaner and scrub with a white nylon pad – this can help break any surface tension created by the penetrating sealer (and may get some of the stains out at the same time. Then rinse and allow to thoroughly dry. After that you are going to have to test with trial and error a to see if you can get such a product to work ok – I suspect you will. You could try Aqua Mix and Mapei USA for starters (you would have to contact their own tech support for their recommendations).
You ought ought be able to achieve what you are looking for regarding the seal. However enhancing/ darkening is going t be tricky as 1) most acrylic top coat sealers do not enhance (they do darken a tiny amount, but not significantly) and 2) the pre existing impregnating sealer will prevent this.
Hope that helps
Ian
Thank you! I’ll look for those.
Hi Ian,
We’ve applied two coats of linseed on handmade terracotta tiles but it hasn’t dried evenly. There are some shiny/sticky patches and some are matt. Have we put too much on, or should we put more on to even it out before we put the beeswax polish on. Or should ever be stripping off the linseed and start again?
Cheers
Hi Peter,
OK, too much, and / or not removing the surplus before it dries. You could try a little more – not because you need more, but rather trying to make use of the solvent in which the linseed is dissolved, to try to re-emulsify the semi set linseed. Time is of the essence though (apologies, I have been out of the country and only just picked this up).
You can also try a plastic scraper to remove the thickets deposits then try the above. If it is softening the linseed, keep rubbing and wipe off with absorbent paper towels – add more if needed to make sure the surface comes clean of residue. then buff to dry with more paper towels.
Failing that you might have to try some white spirit or similar. If the above works then you should not need to re apply any more linseed. If you have to strip with a solvent then you may have to top up the linseed after – just be sure to buff off any remaining oil after bout 20 minutes, before it dries.
Hope that helps
Ian
We applied 2 coats of miracle porous plus to our unglazed natural terra cotta floors and it offered limited protection (and a terrible smell as well). We need to apply more sealer and I’m wondering what may work best that isn’t a wax. Are there any Fila products or other that would be a good sealer or top coat to prevent staining? Currently you spill a cup of water and it takes hours for the water stain to disappear. Preferably the water wouldn’t even absorb or would take a while to at least! Any help is appreciated!
Hi, OK, a solvent-based impregnating sealer is never going to be the right choice for a terracotta, the tile is just way too porous in my opinion. If you wanted an impregnator so as not to alter the look and feel of the tile, then in this case a premium water based product (for example, Aqua Mix Seal Gold or similar) may have worked out better. However I feel for this type of material, certainly for indoor situations, that an impregnator is not the best way. I think you need a coating (yes they have their own issues, they wear, need regular top ups every few years and can impart a slight sheen or even a gloss). As you don’t want a natural wax, I suggest you opt for a synthetic/acrylic coating designed for the material. Aqua Mix used to make one called Seal & Finish Low Sheen – which at the time (and yes I was working for them) I genuinely believed was the best available both in terms of its performance but also the way it looked, still quite natural, for a non- natural product. I don’t know what they offer now, and there are other companies who may have something equally suitable.
Hope this helps
Ian